1. Field of the Invention
The present invention relates to extending local area network (LAN) service over a provider network using a virtual private LAN service (VPLS).
2. Description of the Related Art
Networks of general purpose computer systems and specialized devices connected by external communication links are well known and widely used in commerce. The networks often include one or more network devices that facilitate the passage of information between the computer systems. A network node is a network device or computer or specialized device connected by the communication links. An end node is a node that is configured to originate or terminate communications over the network. An intermediate network node facilitates the passage of data between end nodes.
Information is exchanged between network nodes according to one or more of many well known, new or still developing protocols. In this context, a “protocol” consists of a set of rules defining how the nodes interact with each other based on information sent over the communication links.
A local area network (LAN) comprises multiple end nodes that share a communication link without an intervening intermediate network node. Such a communication link is called a network segment. The nodes on a network segment exchange data packets formatted according to a data link layer protocol such as the Ethernet protocol. A destination or source for a data packet on a network segment is indicated by a Media Access Control (MAC) identifier that is unique among all network devices. A virtual LAN (VLAN) includes one or more intermediate network nodes that forward data packets from one segment to another segment based on an identifier called a tag that indicates segments on the same VLAN. The tag is included in the Ethernet protocol header.
Different LANs and VLANs, administered by different entities and using different communication links, communicate with each other using an internetworking layer protocol, such as the Internet Protocol (IP) or the Multiple-Protocol Label Switching protocol (MPLS).
A virtual private network VPN is made up of one or more LANs administered by one entity, called herein a customer, connected by tunnels across one or more wide area networks administered by one or more different entities, each called a service provider (SP). In network parlance, a tunnel for data is simply a protocol that encapsulates that data. A tunnel is provided by a tunneling protocol, like MPLS, that encapsulates the data link layer protocol data packets and ensures their delivery from one site of the customer to a another site of the same customer. The multiple customer sites can be connected by a full mesh of tunnels connecting each of the customer's LANs and VLANs to every other LAN and VLAN of the same customer. Such a mesh of tunnels is called a virtual private LAN service (VPLS).
In current VPLS approaches, each tunnel is configured to take only the traffic from a single customer. Traffic from other customers is transported across the wide area network using different tunnels. Each tunnel must be configured to indicate a particular interface to the customer equipment at each end, and the type of data to be packed in the tunnel so that it can be correctly unpacked and delivered at the far end. The tunnel is established and disestablished using a tunneling control protocol, such as the label distribution protocol (LDP) for MPLS tunnels. The tunneling control protocol is determined during configuration. Each of the configured point to point tunnels is called a pseudowire (PW).